1. Field of the Invention
The invention relates in general to elevator systems, and more specifically to new and improved apparatus and methods for generating a landing speed pattern for elevator systems.
2. Description of the Prior Art
A speed pattern for an elevator car is usually time based until the car reaches a distance from the target floor at which it must start the slowdown phase of the run. At this point, a distance based slowdown pattern is usually substituted for the time based pattern. When the distance-to-go value from the elevator car to the target floor is based upon updating a counter with pulse wheel generated distance pulses, or when it is determined by any other method in which the car position is not absolute, it is common to switch to a hatch transducer arrangement, such as shown in U.S. Pat. Nos. 2,874,806; 3,138,223; 3,207,265; and 3,507,360. The hatch transducer provides a continuous analog landing speed pattern which starts, for example, when the elevator car reaches a point 10 inches (25.4 cm) from floor level and continues until the car is stopped level with the floor. The hatch transducer includes a pair of car mounted transformers, associated circuitry, and a metallic specially shaped landing vane at each floor. While excellent landings are made using the hatch transducer, it does require substantial time to initially adjust the landing vane at each floor, in order to produce good landings. Also, being analog, the circuitry is subject to manufacturing tolerances and drift, which causes different landing patterns to be produced at different floors, as well as adversely affecting repeatability. Further, while the hatch transducer was designed to compensate for horizontal car motion, i.e., concentrated car loading, the compensation is only partial and zero position is affected.
A digital landing device can overcome the abovementioned problems, but it would introduce new problems. The ideal digital device will detect absolute car position over a .+-.10 inch (25.4 cm) landing zone range, for example, to a resolution of 7 bits. This is difficult and costly to do. The resolution can readily be achieved using an incremental system, but this suffers from not being sure of absolute car position.